libmnl  1.0.4
rtnl-link-event.c
1 /* This example is placed in the public domain. */
2 #include <stdio.h>
3 #include <stdlib.h>
4 #include <unistd.h>
5 
6 #include <libmnl/libmnl.h>
7 #include <linux/if.h>
8 #include <linux/if_link.h>
9 #include <linux/rtnetlink.h>
10 
11 static int data_attr_cb(const struct nlattr *attr, void *data)
12 {
13  const struct nlattr **tb = data;
14  int type = mnl_attr_get_type(attr);
15 
16  /* skip unsupported attribute in user-space */
17  if (mnl_attr_type_valid(attr, IFLA_MAX) < 0)
18  return MNL_CB_OK;
19 
20  switch(type) {
21  case IFLA_MTU:
22  if (mnl_attr_validate(attr, MNL_TYPE_U32) < 0) {
23  perror("mnl_attr_validate");
24  return MNL_CB_ERROR;
25  }
26  break;
27  case IFLA_IFNAME:
28  if (mnl_attr_validate(attr, MNL_TYPE_STRING) < 0) {
29  perror("mnl_attr_validate");
30  return MNL_CB_ERROR;
31  }
32  break;
33  }
34  tb[type] = attr;
35  return MNL_CB_OK;
36 }
37 
38 static int data_cb(const struct nlmsghdr *nlh, void *data)
39 {
40  struct nlattr *tb[IFLA_MAX+1] = {};
41  struct ifinfomsg *ifm = mnl_nlmsg_get_payload(nlh);
42 
43  printf("index=%d type=%d flags=%d family=%d ",
44  ifm->ifi_index, ifm->ifi_type,
45  ifm->ifi_flags, ifm->ifi_family);
46 
47  if (ifm->ifi_flags & IFF_RUNNING)
48  printf("[RUNNING] ");
49  else
50  printf("[NOT RUNNING] ");
51 
52  mnl_attr_parse(nlh, sizeof(*ifm), data_attr_cb, tb);
53  if (tb[IFLA_MTU]) {
54  printf("mtu=%d ", mnl_attr_get_u32(tb[IFLA_MTU]));
55  }
56  if (tb[IFLA_IFNAME]) {
57  printf("name=%s", mnl_attr_get_str(tb[IFLA_IFNAME]));
58  }
59  printf("\n");
60  return MNL_CB_OK;
61 }
62 
63 int main(void)
64 {
65  struct mnl_socket *nl;
66  char buf[MNL_SOCKET_BUFFER_SIZE];
67  int ret;
68 
69  nl = mnl_socket_open(NETLINK_ROUTE);
70  if (nl == NULL) {
71  perror("mnl_socket_open");
72  exit(EXIT_FAILURE);
73  }
74 
75  if (mnl_socket_bind(nl, RTMGRP_LINK, MNL_SOCKET_AUTOPID) < 0) {
76  perror("mnl_socket_bind");
77  exit(EXIT_FAILURE);
78  }
79 
80  ret = mnl_socket_recvfrom(nl, buf, sizeof(buf));
81  while (ret > 0) {
82  ret = mnl_cb_run(buf, ret, 0, 0, data_cb, NULL);
83  if (ret <= 0)
84  break;
85  ret = mnl_socket_recvfrom(nl, buf, sizeof(buf));
86  }
87  if (ret == -1) {
88  perror("error");
89  exit(EXIT_FAILURE);
90  }
91 
92  mnl_socket_close(nl);
93 
94  return 0;
95 }